There is an issue, that VFP is not using indexes using STR() for rushmore optimization. But nevertheless, they work. Although an index expression should have fixed length an index on Alltrim(field) works too, VFP intelligently pads it to the field length and you have the benefit of striping off leading whitespace.

Maybe DTOC is making problems. Have you SET SYSFORMATS ON? How are your date settings? Your index expression depends on much settings, which can cause errors.

Its much better to define the index with this expression:
SET COLLATE TO "MACHINE"
INDEX ON DTOS(dField)+BINTOC(nField)+cField TAG whatever additve

Bye, Olaf.